Polyurethane foams are widely known and used in automotive, housing and other industries. Such foams are produced by reaction of a polyisocyanate with a polyol in the presence of a catalyst, typically a tertiary amine. Unfortunately, tertiary amine catalysts are usually malodorous and offensive, and many have high volatility due to their low molecular weight. To overcome this problem, polyurethane manufacturers have sought to achieve near zero amine emissions by using “non-fugitive” tertiary amine catalysts, which remain in the foam during and after formation. The retention is typically due to either low volatility or to reaction with other components of the composition. The latter variety typically remain in the foam due to the presence of an isocyanate-reactive group such as a primary or secondary amine, a hydroxyl, or other reactive group that ties them to the foam. Whether due to low volatility or by reaction with the polyurethane, use of non-fugitive tertiary amine catalysts greatly reduces amine emissions from the polyurethane, but has the unfortunate effect of reducing the stability of the polyurethane under humid aging conditions. For example, foams based on 4,4′-diphenylmethane diisocyanate (MDI) may barely meet typical specification requirements after humid aging, and foams based on toluene diisocyanate (TDI) may completely fail to meet specifications. In general, foams made with any tertiary amine catalyst that remains in the foam tend to exhibit poor humid aged physical properties. Such deterioration may be so severe as to make the foams unsuitable for use, for instance in automotive applications. Therefore, it would be desirable to overcome performance deterioration in polyurethane foams made with non-fugitive tertiary amine catalysts.
U.S. Pat. No. 5,173,516 discloses the preparation of high resiliency polyurethane foams characterized by high strength and load bearing properties.
U.S. Pat. No. 6,660,783 also discloses the preparation of high resilient flexible slabstock polyurethane foams having improved aging resistance to heat and moisture, in particular improved wet compression set (WCS) and humid aged compression set (HACS), and having sufficient rigidity.
U.S. Pat. No. 4,210,728 discloses a reactive polyol composition useful in the preparation of high resilient polyurethane foams comprising a polyol and from 0.5 to 5.0 wt % of a reactive cycloaliphatic diamine.